They'll fit perfectly fine without any modifications as long as you have a 980 BIGFOOT (both the tall tub and the very tall tub version), but they will not fit on a 950......this is the model that came with the 21x11x8 Goodyear Rawhides. 25" tires are is the biggest you can go on those.
The ASX's are THE BEST AATV TIRE OUT THERE, end of story. Here's mine: